TW201704408A - Adhesive tape and method for producing adhesive tape - Google Patents

Abstract

The purpose of the present invention is to provide: an adhesive tape which has excellent heat resistance and is not susceptible to increase of the adhesive force even after a long period of time or at high temperatures; and a method for producing this adhesive tape. The present invention is an adhesive tape having a base layer and an adhesive layer, and wherein the adhesive layer contains a styrene elastomer and has a gel fraction of 70% by weight or more.

Description

Adhesive tape and adhesive tape manufacturing method

The present invention relates to an adhesive tape which is excellent in heat resistance and which is not easily cured by adhesion over time or at a high temperature, and a method of producing the adhesive tape.

Adhesive tapes are used in various industrial fields because they can be easily joined. In the field of construction, adhesive tape is used for temporary fixing of maintenance sheets, bonding of interior materials, etc. In the automotive field, fixings of interior parts such as sheets and sensors, side trims, side window shades Adhesive tapes are used in the fixing of exterior parts, etc. In the field of electrical and electronic applications, adhesive tapes are used for assembly of modules, bonding of housings of modules, and the like. Further, as a surface protective material for temporarily protecting the surface of a member such as an optical device, a metal plate, a coated metal plate, a resin plate, or a glass plate, an adhesive tape is also used.

For the adhesive tape, various properties such as mechanical properties such as tensile strength or appropriate adhesion are required depending on the use. For example, in applications exposed to high temperatures, high heat resistance is not important in the high temperature environment. Further, in the use as a surface protective material, it is required that the film may not be adhered with time or at a high temperature, and the resin may be peeled off without leaving a paste (low adhesion enhancing property).

As an adhesive tape excellent in heat resistance or low adhesion enhancement, it is known to contain polybenzazole. The oxygen-based adhesive composition is used as an adhesive tape for an adhesive component (for example, Patent Document 1). However, conventionally known adhesive tapes having excellent heat resistance are usually produced by a so-called coating method in which a solution in which an adhesive component is dissolved in a suitable organic solvent is applied to a substrate and dried to form an adhesive layer. The adhesive tape produced by such a coating method has a problem that residual organic resin is left in the adhesive layer to cause paste residue.

[Previous Technical Literature]

[Patent Literature]

Patent Document 1: Japanese Patent Laid-Open Publication No. 2003-96429

The present inventors have studied the use of a styrene-based elastomer as an adhesive component of an adhesive layer constituting an adhesive tape. The adhesive layer containing a styrene-based elastomer can exhibit high initial adhesion, and can be formed by a lamination method such as extrusion lamination or extrusion coating, or an extrusion molding method, and the like, so that no organic solvent can be used. Easy to make adhesive tape. However, the adhesive layer containing a styrene-based elastomer has a problem of poor heat resistance, and subsequent reinforcement occurs over time or at a high temperature.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an adhesive tape which is excellent in heat resistance and which is not easily cured with an adhesive force over time or at a high temperature, and a method of producing the adhesive tape.

The present invention relates to an adhesive tape comprising a base material layer and an adhesive layer, wherein the adhesive layer contains a styrene-based elastomer, and the adhesive layer has a gel fraction of 70% by weight or more.

The invention is described in detail below.

As a result of intensive studies, the inventors of the present invention have found that an adhesive tape having a gel fraction of a styrene-based elastomer adjusted to have a gel fraction of 70% by weight or more is excellent in heat resistance and has a tendency to pass over time or at a high temperature. The adhesiveness is also not easily enhanced with low adhesion enhancement, thereby completing the present invention.

The adhesive tape of the present invention has a substrate layer and an adhesive layer.

The above adhesive layer contains a styrene-based elastomer. By using a styrene-based elastomer as an adhesive component, an adhesive tape having excellent initial adhesion can be produced by an extrusion molding method without using an organic solvent.

In order to make the adhesive fraction of the adhesive layer of the adhesive tape of the present invention 70% by weight or more, a styrene-based elastomer having a polymerizable double bond is preferably used as the styrene-based elastomer to be used as a raw material. A styrene-based elastomer having a polymerizable double bond can be used as the styrene-based elastomer, and an adhesive layer can be formed by an extrusion molding method or the like, and then the styrene-based elastomer having a double bond can be crosslinked. This adjusts the gel fraction of the adhesive layer to 70% by weight or more.

The styrene-based elastomer having a polymerizable double bond is not particularly limited, and examples thereof include a styrene-isoprene block copolymer (SI) and a styrene-isoprene-styrene block. Copolymer (SIS), styrene-butadiene block copolymer (SB), styrene-butadiene-styrene block copolymer (SBS), partially hydrogenated styrene-ethylene butylene-styrene block Copolymer (partially hydrogenated SEBS), partially hydrogenated styrene-ethylene propylene-styrene block copolymer (partially hydrogenated SEPS), and the like.

The pressure-sensitive adhesive layer may contain, as a raw material, another resin other than the styrene-based elastomer having a polymerizable double bond.

The other resin is not particularly limited, and examples thereof include hydrogenated styrene-ethylene butylene-styrene block copolymer (hydrogenated SEBS), hydrogenated styrene-ethylene propylene-styrene block copolymer (hydrogenated SEPS), and the like. a styrene-based elastomer having no polymerizable double bond; or a non-styrene-based elastomer having a polymerizable double bond such as syndiotactic 1,2-polybutadiene (RB); or polyethylene (PE) or polybutylene An olefin-based resin having no polymerizable double bond, such as an olefin, an ethylene-propylene copolymer, an ethylene-butene copolymer, or a propylene-butene copolymer.

In the case where the pressure-sensitive adhesive layer contains another resin, the content of the styrene-based elastomer having a polymerizable double bond in the entire elastomer is preferably 60% by weight or more. By setting the content of the styrene-based elastomer having the polymerizable double bond to 60% by weight or more, the gel fraction of the pressure-sensitive adhesive layer can be more easily adjusted to 70% by weight or more. The content of the styrene-based elastomer having a polymerizable double bond is more preferably 70% by weight or more, and may be 100% by weight.

The above adhesive layer may further contain an adhesion-imparting agent.

The adhesion-imparting agent is not particularly limited, and examples thereof include petroleum-based resins such as aliphatic copolymers, aromatic copolymers, aliphatic aromatic copolymers, and alicyclic copolymers; and kumquat-anthraquinone resins; terpenes; Resin; phenolic resin; rosin resin such as polymeric rosin; (alkyl) phenol resin; xylene resin.

The hydrogenation rate of the above-mentioned adhesion-imparting agent is not particularly limited, and any of an unhydrided product, a partially hydrogenated product, and a completely hydrogenated product can be used.

Further, an adhesion-imparting agent commercially available as a mixture with a polyolefin resin can also be used. These adhesion-imparting agents may be used singly or in combination of two or more.

The content of the above-mentioned adhesion-imparting agent is not particularly limited, and a preferred upper limit of 100 parts by weight of the above elastomer component is 50 parts by weight. If the content of the above adhesion-imparting agent exceeds 50 In the case of parts by weight, there is a case where the adhesion-imparting agent oozes out from the adhesive layer. A more preferable upper limit of the content of the above adhesion-imparting agent is 40 parts by weight.

In the case where the above-mentioned adhesive layer is subjected to light irradiation when the gel fraction of the adhesive layer is adjusted to 70% by weight or more, it is preferred to contain a photopolymerization initiator.

The photopolymerization initiator is not particularly limited, and for example, a benzophenone compound, an acetophenone compound, a mercaptophosphine oxide compound, a titanocene compound, an oxime ester compound, and a benzoin ether can be preferably used. Compound, 9-oxosulfur Wait.

The above adhesive layer may contain a release agent in a range that does not inhibit the effects of the present invention. When the release agent is contained, for example, for use as a surface protective material, the residue of the paste at the time of peeling can be further prevented. The release agent is not particularly limited, and a conventionally known release agent can be used.

When the adhesive layer contains a release agent, the upper limit of the content of the release agent relative to 100 parts by weight of the elastomer component is preferably 0.5 part by weight. When the content of the above-mentioned release agent exceeds 0.5 part by weight, the release agent may bleed out from the adhesive layer to contaminate the surface of the adherend.

The above-mentioned adhesive layer may optionally contain a conventionally known additive such as a softening agent, an antioxidant, and a reinforcing agent.

The gel fraction of the above adhesive layer is 70% by weight or more. By setting the gel fraction of the above adhesive layer to 70% by weight or more, the adhesive tape of the present invention can exhibit high heat resistance and can exhibit low adhesion which is not easily enhanced by adhesion over time or at a high temperature. Enhancement. The gel fraction of the above adhesive layer is more preferably 75% by weight or more, still more preferably 80% by weight or more. The upper limit of the gel fraction of the pressure-sensitive adhesive layer is not particularly limited, and the gel fraction of the pressure-sensitive adhesive layer is preferably 98% by weight or less in order to secure a good initial adhesion.

Further, the gel fraction was measured as follows. First, the adhesive tape was taken out from the adhesive tape, and cut into a rectangular shape of about 50 mm × 100 mm to prepare a test piece. The test piece was immersed in toluene at 23 ° C for 24 hours, and then taken out from the toluene at 110 ° C. Dry for 1 hour. The weight of the test piece after drying was measured, and the gel fraction was calculated using the following formula (1). Further, the test piece was not laminated to protect the release film of the adhesive layer.

Gel fraction (% by weight) = (W2/W1) × 100 (1)

(W1: weight of the test piece before immersion, W2: weight of the test piece after immersion and drying)

Further, when it is not possible to ensure a sufficient sample amount, the self-adhesive tape can be taken out only by the adhesive layer, and cut into a rectangular rectangular test piece of about 5 mm × 10 mm to measure the gel fraction.

The temperature at which the storage elastic modulus E' of the pressure-sensitive adhesive layer is 1.0 × 10 ⁵ Pa is preferably 130 ° C or higher. Thereby, when attached to the adherend, it is possible to further suppress the subsequent reinforcement from occurring over time or at a high temperature. The temperature at which the storage elastic modulus E' of the above-mentioned adhesive layer is 1.0 × 10 ⁵ Pa is more preferably 135 ° C or higher.

The storage elastic modulus E' of the above adhesive layer at 150 ° C is preferably 6.0 × 10 ⁵ Pa or more. Thereby, when attached to the adherend, it is possible to further suppress the subsequent reinforcement from occurring over time or at a high temperature.

Further, the storage elastic modulus E' of the above-mentioned adhesive layer can be, for example, a viscoelastic spectrometer such as DVA-200 (manufactured by IT Meter. and ° Control Co., Ltd.), and 10 ° C/min, 10 Hz in a constant-speed heating mode. The dynamic viscoelastic spectrum of the above adhesive layer was measured under the conditions.

The method of adjusting the temperature at which the storage elastic modulus E' of the pressure-sensitive adhesive layer is 1.0 × 10 ⁵ Pa to 130 ° C or higher, and adjusting the storage elastic modulus E' at 150 ° C to 6.0 × 10 ⁵ Pa or more The method is not particularly limited, and examples thereof include a method of crosslinking an adhesive layer.

The thickness of the pressure-sensitive adhesive layer is not particularly limited as long as it is appropriately set depending on the application, and a preferred lower limit is 2 μm, and a preferred upper limit is 30 μm. When the thickness of the pressure-sensitive adhesive layer is less than 2 μm, sufficient initial adhesion may not be exhibited. When the thickness of the pressure-sensitive adhesive layer exceeds 30 μm, the adhesive strength is increased, which is not suitable for applications such as peeling of a surface protective material. A more preferable lower limit of the thickness of the above adhesive layer is 3 μm, and a more preferable upper limit is 20 μm.

The base material layer is not particularly limited, and preferably contains a polyolefin resin.

The polyolefin resin is not particularly limited, and a conventionally known polyolefin resin can be used, and examples thereof include polypropylene (PP) and polyethylene (PE).

Examples of the polypropylene include homopolypropylene, atactic polypropylene, and block polypropylene.

Examples of the polyethylene include high pressure low density polyethylene, linear low density polyethylene, and high density polyethylene.

In the case where the electron beam irradiation is carried out when the gel fraction of the adhesive layer is adjusted to 70% by weight or more, the base material layer composed of block polypropylene and/or polyethylene is preferable. The base material layer composed of the block polypropylene and/or polyethylene is less likely to be embrittled even when irradiated with an electron beam, and can maintain high tensile strength.

The base material layer may contain an antistatic agent, a mold release agent, an antioxidant, a weathering agent, a crystallization nucleating agent or the like in a range that does not impair the effects of the present invention; a resin such as a polyolefin, a polyester, a polyamide or an elastomer; Modifier.

The thickness of the base material layer is not particularly limited as long as it is appropriately set depending on the application, and a preferred lower limit is 25 μm, and a preferred upper limit is 200 μm. If the thickness of the above substrate layer When the thickness is less than 25 μm, the adhesiveness of the adhesive tape is weak and the handleability is poor. When the thickness is more than 200 μm, the roll may be wound into a roll and the wound may remain. A more preferred lower limit of the thickness of the substrate layer is 30 μm, and a more preferred upper limit is 150 μm.

Preferably, the adhesive tape of the present invention is adhered to the corona-treated surface of the corona-treated plastic film on the surface, and after being placed at 40 ° C for 24 hours, the adhesive tape is peeled off, and the plastic film before and after bonding is applied. The rate of change in surface tension of the surface subjected to corona treatment was 35% or less. When the surface of the adherend is contaminated and the surface tension is lowered, when an adhesive or a hard coating agent is applied to the surface of the adherend after peeling off the adhesive tape, minute coating unevenness occurs, and when it is assembled in the product, A situation in which brightness or color unevenness is poor. The rate of change of the surface tension can be adjusted, for example, by adjusting the amount of addition of a release agent or the like added to the adhesive layer.

The method for producing the adhesive tape of the present invention is not particularly limited. For example, the unadjusted adhesive layer may be adjusted after the laminate having the unadjusted adhesive layer having an unadjusted gel fraction laminated on the base material layer. The method of gel fraction and the like.

Moreover, the manufacturing method of the adhesive tape is also one of the inventions, and the manufacturing method of the adhesive tape is the adhesive layer which has the base material layer and the styrene-type elastomer, and the adhesive layer has the gel fraction of 70 weight. a method of adhesive tape of more than %, and having the steps of: preparing a laminate having an unadjusted adhesive layer having an unadjusted gel fraction on the substrate layer; and an unadjusted gel to the laminate The unadjusted adhesive layer of the fraction is irradiated with the active energy ray so that the gel fraction of the adhesive layer is 70% by weight or more.

As a method of preparing the above-mentioned laminated body, for example, a coextrusion molding method in which each of the base material layer and the pressure-sensitive adhesive layer is supplied to a plurality of extruders is used, or a T-die is formed or blown in advance. On the substrate layer obtained by expansion molding, by extrusion lamination, extrusion coating, etc. A method of laminating an unadjusted adhesive layer by a known lamination method, or a method of laminating the respective layers obtained by dry lamination after separately forming the layers. Among them, in terms of productivity, a coextrusion molding method is preferred.

The method of adjusting the gel fraction is not particularly limited. When the unadjusted adhesive layer contains the styrene elastomer having a polymerizable double bond, an active energy ray such as an electron beam or light may be irradiated. Further, the styrene-based elastomer having a polymerizable double bond is crosslinked. Among them, a method of irradiating an electron beam is preferred in that it is not necessary to use a photopolymerization initiator in combination and a reaction rate is high and the initial gel fraction can be achieved in a short time.

The method of irradiating the electron beam is not particularly limited, and for example, a commercially available electron beam irradiation apparatus such as Curetron R manufactured by NHV Corporation, Inc., can be used to irradiate the unadjusted adhesive layer of the laminate. method.

The conditions of the electron beam irradiation may be appropriately set according to the type or content of the styrene-based elastomer having the polymerizable double bond, and the like, and the acceleration voltage is preferably from 50 to 1000 kV and the dose is from about 0.5 to 10 Mrad.

Since the adhesive tape of the present invention can be easily produced by a production method in which an organic solvent is not used, such as an extrusion molding method, the problem of residual organic solvent can be solved. Moreover, by adjusting the gel fraction of the adhesive layer to 70% by weight or more, it is possible to exhibit heat resistance and low adhesion enhancement which is not easily enhanced with adhesion over time or at a high temperature.

The adhesive tape of the present invention is particularly useful for applications exposed to high temperature environments. Further, even if it is set to a relatively high initial adhesive force, it does not increase with time or at a high temperature, and it can be peeled off without leaving a paste, so that it can be preferably used as a surface protective material. For example, an optical member for a liquid crystal display such as a ruthenium sheet (also referred to as a brightness enhancement film) or a diffusion film has a concave surface on the surface. a convex shape, but if it is the adhesive tape of the present invention, even if it adheres to the surface of such uneven shape with a high initial adhesive force, the adhesive force is not easily enhanced over time or at a high temperature, so that the paste does not remain. Easily peeled off.

According to the present invention, it is possible to provide an adhesive tape which is excellent in heat resistance and which is not easily cured with adhesion over time or at a high temperature, and a method of producing the adhesive tape.

Hereinafter, the aspects of the present invention will be described in more detail by way of examples, but the invention is not limited to the examples.

(Example 1)

As a raw material of the adhesive layer, an adhesive-imparting agent (trade name "Arkon P125", manufactured by Arakawa Chemical Industries Co., Ltd.) was prepared in an amount of 100 parts by weight of the resin A shown in Table 1 as a styrene-based elastomer having a polymerizable double bond. 5 parts by weight of an alicyclic saturated hydrocarbon resin and 1 part by weight of an antioxidant (trade name "IRGANOX 1010", manufactured by BASF Corporation) were used to obtain an adhesive composition for forming an adhesive layer.

80 parts by weight of a block polypropylene (trade name "J715M", manufactured by Prehmann Polymer Co., Ltd.) and 20 parts by weight of low density polyethylene (trade name "L2340", manufactured by Asahi Kasei Co., Ltd.) were mixed as a raw material of the base material layer.

Co-extrusion molding was carried out by a T-die method to obtain a laminate having a thickness of the substrate layer of 55 μm and a thickness of the uncrosslinked adhesive layer of 5 μm.

From the side of the uncrosslinked adhesive layer of the obtained laminate, an electron beam irradiation apparatus (trade name "Caretron R", manufactured by NHV Corporation) was used to irradiate electrons at an acceleration voltage of 500 kV and a dose of 5 Mrad. bundle. The gel fraction of the adhesive layer of the adhesive tape after the electron beam irradiation was measured and found to be 75% by weight.

Further, for the adhesive layer of the adhesive tape after the electron beam irradiation, a viscoelastic spectrometer (manufactured by IT Meter. and Control, DVA-200) was used, and the conditions of 10 ° C/min and 10 Hz in the constant temperature heating mode were employed. The dynamic viscoelastic spectrum was measured to determine the storage elastic modulus E'. As a result, the storage elastic modulus E' became 1.0×10 ⁵ Pa at a temperature of 145° C. or higher, and the storage elastic modulus E′ at 150° C. was 8×10. ⁵ Pa.

(Examples 2 to 6, Comparative Examples 1 to 6, Reference Example 1)

The adhesive tape was obtained in the same manner as in Example 1 except that the materials of the adhesive layer and the substrate layer and the irradiation conditions of the electron beam were as shown in Table 1 and Table 2.

Further, as the release agent, exoethyl bis-lipidamine (manufactured by NOF Corporation, trade name "Alflow H50F") was used.

<evaluation>

The adhesive tapes obtained in the examples, comparative examples, and reference examples were subjected to the following evaluations. The results are shown in Table 2.

(1) Evaluation of initial adhesion

A crepe sheet (a diffusion film of an acrylic film having an arithmetic mean roughness Ra (JIS B 0601-1994) of 0.32 μm) was prepared as an adherend. A 25 mm wide adhesive tape was attached to cover the matte side of the adherend to prepare a test piece. The attachment was carried out by pressing at a speed of 300 mm/min using a 2 kg pressure-bonding rubber roller in an environment of 23 ° C and a relative humidity of 50% RH. The obtained test piece was allowed to stand in an environment of 23 ° C and a relative humidity of 50% RH for 30 minutes. After the placement, the adhesive tape was peeled off from the adherend at a stretching speed of 300 mm/min in the direction of 180° in accordance with JIS Z0237, and the initial adhesive force was measured. Further, the initial adhesion was determined based on the following criteria.

◎: 0.15N/25mm or more and less than 0.3N/25mm

○: 0.1 N/25 mm or more and less than 0.15 N/25 mm, or 0.3 N/25 mm or more and less than 0.4 N/25 mm

×: not up to 0.1N/25mm or 0.4N/25mm or more

(2) Evaluation of adhesion enhancement rate

A crepe sheet (a diffusion film of an acrylic film having an arithmetic mean roughness Ra (JIS B 0601-1994) of 0.32 μm) was prepared as an adherend. A 25 mm wide adhesive tape was attached to cover the matte side of the adherend to prepare a test piece. The attachment was carried out by laminating at a speed of 300 mm/min using a 2 kg pressure-bonding rubber roller in an environment of 23 ° C and a relative humidity of 50% RH. The obtained test piece was allowed to stand at a temperature of 50 ° C for 168 hours. After being placed, the test piece is taken out to room temperature, and after being left for 60 minutes, it is pulled from the adherend according to JIS Z0237. The adhesive tape was peeled off at a stretching speed of 300 mm/min in the direction of 180°, and the adhesiveness over time was measured.

Using the initial adhesive force and the time-dependent adhesive force obtained by the above formula (1), the rate of change from the initial adhesive force to the temporal adhesive force (adhesion enhancement ratio) was calculated by the following formula.

Rate of change (adhesion enhancement rate) (%) = (time-dependent adhesion / initial adhesion) × 100

Further, the temporal adhesion was determined based on the following criteria.

◎: 150% or less

○: more than 150% and less than 200%

×: 200% or more

(3) Evaluation of heat resistance

The prepared adhesive tape was attached to a stainless steel plate, and a load of 200 g was applied to the adhesive surface, and the holding time of 120 ° C was measured. Further, heat resistance was determined based on the following criteria.

◎: 30 minutes or more

○: more than 5 minutes and less than 30 minutes

×: 5 minutes or less

(4) Evaluation of the surface tension of the surface of the adherend after peeling

The adhesive tape prepared was attached to the corona treated polyethylene terephthalate at a rate of 300 mm/min at a temperature of 23 ° C and a relative humidity of 50% using a 2 kg crimping rubber roller. (PET) film. It was placed in an oven at 40 ° C for 24 hours in this state. After taking out to room temperature and leaving it for 60 minutes, the adhesive tape was peeled off.

The surface tension of the surface of the PET film before and after the peeling was measured by the method specified in JIS K6768 using the mixed liquid for the wetting tension test, and the surface tension reduction rate was calculated by the following formula and evaluated according to the following criteria.

Surface tension reduction rate = (1 - (surface tension after peeling / surface tension before attachment)) × 100

○: The surface tension reduction rate is 35% or less

×: The surface tension reduction rate exceeds 35%

(5) Evaluation of tensile strength

The prepared adhesive tape was cut to 10 mm, and the tensile strength was measured at a speed of 300 mm/min using a Tensilon universal testing machine (trade name "RTF-1210", manufactured by A&D Co., Ltd.). Further, the tensile strength was determined based on the following criteria.

◎: 40MPa or more

○: 30 MPa or more and less than 40 MPa

×: less than 30 MPa

[Industrial availability]

According to the present invention, it is possible to provide an adhesive tape which is excellent in heat resistance and which is not easily cured with adhesion over time or at a high temperature, and a method of producing the adhesive tape.

Claims (5)

An adhesive tape comprising a base material layer and an adhesive layer, wherein the adhesive layer contains a styrene-based elastomer, and the adhesive layer has a gel fraction of 70% by weight or more. The adhesive tape of claim 1, wherein the adhesive layer has a storage elastic modulus E' of 6.0 × 10 ⁵ Pa or more at 150 °C. The adhesive tape of claim 1 or 2, wherein the adhesive tape is attached to the corona-treated surface of the corona-treated plastic film, and the adhesive tape is peeled off after being left at 40 ° C for 24 hours. The rate of change in surface tension of the corona-treated surface of the above-mentioned plastic film before and after bonding was 35% or less. The adhesive tape of claim 1, 2 or 3, wherein the substrate layer is composed of block polypropylene and/or polyethylene. A method for producing an adhesive tape, comprising: a method of producing an adhesive tape having a base layer and an adhesive layer containing a styrene elastomer and having a gel fraction of 70% by weight or more of the adhesive layer, wherein a step of: preparing a laminate having an unadjusted adhesive layer having an unadjusted gel fraction on the substrate layer; and adjusting the unadjusted gel fraction of the laminate to an unadjusted adhesive layer The active energy ray has a gel fraction of the above adhesive layer of 70% by weight or more.